Both linear and rotary filling plants are known to comprise a plurality of serially arranged operating units for the bottles to be moved therethrough. Plastic (PET) bottles, particularly, are moved by being hooked at the neck by means of suitable grippers that are usually made of steel or resistant plastic. These grippers are controlled by suitable cams, which provide to close them around a bottle neck in the gripping stations, and then hold the same in this condition throughout the pathway to the release station.
The bottles, however, sometimes happen to be entangled in parts of the machine. In this event, though becoming deformed, they do not break, and thus act as levers on the gripper that is locked by the cam in a closed condition, and cause serious damage to it. While steel grippers can be deformed, plastic grippers are easily broken, which implies that the latter have to be frequently replaced.